Agilent Technologies 655 A Series - Page 93

Principles of Operation 93
The isolator board includes three separate optical isolator circuits that isolate the front panel signals: RxD, TxD, and PCLR*
signals from the SRx, BSTx and SPCLR* signals at the secondary interface circuits.
Figure 4-8. +5 V BIAS and PCLR* Timing Sequence